It’s not just ignorance. Plain ignorance is normally corrected by education. In the case of grammar and spelling, people actually get DEFENSIVE about doing things wrong. “I’m not writing a college essay, you know what I was trying to say” is a common retort when somebody’s spelling or grammar is pointed out to be incorrect. If you can’t even remember the correct rules of written speech in a single language (your NATIVE LANGUAGE), you really ought to step back and consider whether or not you’re really as smart as you think you are.